“It was beautiful, there was no other way to look at it” Andy thought as she gazed at the thousands of glittering objects she could see from her window of the tram climbing its way to orbit. Intellectually she knew that most were just small satellites, ranging from broadband internet providers to clusters of what she could only suspect were imaging constellations which used a machine learning algorithm to stitch the images of each individual sensor into an ultra-high definition image of the surface.
Knowing these things didn’t make seeing them up close any less impressive. Andy chuckled to herself “good thing I am so easily impressed, otherwise this three day trip be unbearable.” Already she had seen a thunderstorm from the top and a launch from the nearby space launch facility. “I’ll bet that launch was one of those classified government programs that was forbidden by law from using the space elevator” she mused.
Andy was headed to orbit as a senior mineral consultant for Asteroeidḗs Extraction (AE), a multi-national mining corporation. AE was one of the big three companies dominating activity outside cislunar space. The low cost of ‘playing’ in space meant that there were literally thousands of companies vying for attention between the Earth and the Moon supplying everything from communication, to fuel, to what passed for purified water. However that very diversity of industry ensured the cost and risk of moving beyond view of Earth were both prohibitive. Only a handful of governments had even launched small teams beyond Mars, and all of those were temporary trips.
As Andy neared orbit she began to feel what humans have always felt as they gazed on the stars…the limitless possibilities associated with viewing the infinite. ‘Maybe one day’ she thought, ‘maybe one day I’ll make it even further out there.’
The Real Deal
A three day elevator trip, really?
It sounds excruciatingly slow, especially to all of you who already hate getting into a couple minute elevator ride to your hotel room. Remember though – it takes you a couple minutes to get to the top of your hundred, or couple hundred foot tower. Getting to geosynchronous orbit is going to take just a tad longer.
First off – while we talked a bit about orbital scale elevators in previous posts, we haven’t really explored how they work.
For starters they work exactly like the elevator in your hotel does. There is an anchor at the top, connected to one or multiple cars and those cars are raised or lowered on demand along cabling. Seems simple enough. The main difference between an orbital elevator and a hotel one is the length of the cable, and the size / placement of the anchor.
A huge problem with the anchor is that it will not be fixed. After all there isn’t anything in space to ‘hold onto’. So the anchor will have to be an orbital installation of some kind. Its exact size and mass requirements will vary depending on the amount of cargo it will haul. What won’t vary is the orbit it sits in. An object in low earth orbit (LEO) circumnavigates the globe nearly 20 times a day; while a similar object in mid-earth orbit (MEO) will do so between 2-12 times a day. This is a problem if you want your elevator to start and end at the same place since at best your orbital ‘top floor’ will only be over the ‘ground floor’ for an hour or so.
Solving this means putting the elevator anchor in geosynchronous orbit (GEO) which is about 22,236 miles up. Before we turn to the math involved to figure out how long a trip this would be I should note that is whats known as a ‘long way up’.
Ok ok – I know some of you are thinking how will a guy who was on a competitive math team growing up explain math to us simply. This is a fair concern, since some of my former teammates and coaches went on to be theoretical mathmaticians. I on the other hand did not. I learned in that experience that (1) math is easier when you have shortcuts, and (2) I wanted the shortest possible path through the math.
Because of those lessons lets take the short path through the math involved here.
Step 1: Elevator Speed
- Q1: How fast does a ‘regular’ elevator go
- A1: Don’t know…let me check google
- A1a: 15-22 meters per second
- Q2: WTF does that mean in American?
- A2: Uhhh…fast?
- A2a(after a google conversion): 50-70 feet per second
Step 2: Height of Top Floor
- Q: How high is the top floor
- A: Ha! I have that answer because GEO is at 22,236 miles.
- Q2: How many feet is that?
- A2: Damn it
- A2a (post calculator): 117,406,080 feet
Step 3: Divide Height By Speed To Get Time
- Q: What is 117,406,080 feet divided by 50-70 feet per second
- A: 1,677,229 – 2,348,121 seconds
- Q2: What is that in usable units?
- A2: 27,953.8 – 39,135 minutes
- A2a: 465.9 – 652.3 hours
- A2b: 19 – 27 days
As you might have noticed the above result does not get us to what I mentioned above (~3 day trip to orbit). The reason for this is twofold. First off – while the anchor for the elevator needs to be in GEO, the actual ‘top floor’ can be at lower orbits, although doing so will require a bit more engineering than I am comfortable handling on my own.
Second, the primary limitation on elevators here on the ground is the time required to stop the elevator. So an elevator could theoretically go significantly faster if it had literally hundreds of miles of distance to stop. And yes we could have calculated the actual amount of time an elevator would have to accelerate and decelerate on a space elevator…but that is a shit ton of math that I don’t have time for.
Next time we will continue exploring this brave new pre-history of space. Check back soon for updates or head over to my nutrition blog and check it out. Until then – may the light of science guide you on your journey.